Over the years, we’ve talked about the i8 versions that never were. For example, BMW aficionados will remember the hydrogen prototype with a fuel cell. An even spicier idea left on the proverbial cutting room floor was a V10-powered machine using the high-revving S85 engine. There were also rumors of a four-cylinder variant, but that didn’t materialize either.
Ultimately, the plug-in hybrid sports car had to make do with a three-cylinder engine. Yes, the tiny-but-mighty B38 from MINIs and BMW’s smallest cars. It’s been six years since the last i8 was built, and now a mad genius is doing the unthinkable: a B58 engine swap. Trevor from Bimmer Network is attempting to shoehorn a six-cylinder into Munich’s radical sports car.
The inline-six comes from a crashed 2017 M340i xDrive donor car, and this is where the story takes an interesting twist. The turbocharged 3.0-liter unit will be crammed under the hood, where BMW never intended to mount a combustion engine. That’s only possible by removing the front-mounted electric motor, which is already out of the car.
This Frankenstein i8 has already shed its battery pack. Additionally, the tiny 1.5-liter gasoline engine is also gone to make room for the new hardware. However, marrying the M340i’s oily bits to the i8 requires new subframes. These will have to be custom-made for this wild build. The original front and rear subframes have already been removed, following BMW’s service bulletin.
The number one question on everyone’s mind is: Will the B58 fit? Stuffing the M340i’s hardware into a car that once housed a mid-mounted battery and a rear-mounted gas engine sounds incredibly challenging given the packaging constraints. The six-cylinder is expected to sit right above the front axle. The transmission and transfer case will occupy the space where the hybrid battery used to be.
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BMW once built a hydrogen fuel cell i8 Over the years, we’ve talked about the i8 versions that never were. For example, BMW aficionados will remember the hydrogen prot...
Assuming the project comes to fruition, one has to wonder how mounting an inline-six up front will affect weight balance, and, by extension, handling. Trevor is hopeful the distribution won’t change drastically compared to the original i8, as the radiators and auxiliary cooling components will be positioned at the rear.
Ideally, this bonkers i8 will produce around 700 horsepower at the wheels. We’ll certainly be watching how the build progresses in the coming weeks. The idea of a non-electrified i8 with a larger engine remains intriguing even years after production ended. Placing the B58 up front is unconventional, but then again, the i8 was always a hugely complex car built around a plug-in hybrid setup with a small rear-mounted ICE and a front electric motor.
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First published by https://www.bmwblog.com
Source: https://www.bmwblog.com/2026/02/24/bmw- ... gine-swap/